The present invention relates to a rotor construction of a magnetic bearing for use with high-speed rotation machinery.
Magnetic bearings are utilized in machines rotated at high speed (e.g. a centrifugal separator, a turbo machine, etc.) and offer the advantages of no mechanical contact between the rotary and stationary parts, low friction torque and no need of lubrication. As shown in FIGS. 1 and 2, a radially controlled type bearing arranges an electromagnet 1 in the radial direction to control the attractive power of the electromagnet by an electric control device (not shown) so as to support a rotor 2 in an air gap between the electromagnet and the rotor. An iron core of the electromagnet 1 and a rotor armature 3 are made of laminated soft magnetic materials (mainly of silicon iron) having excellent electro-magnetic characteristics in order to minimize excess current loss.
In the electromagnet 1, which is stationarily fixed, the material of the laminated plate can be selected by taking into account only the electromagnetic characteristics.
In the rotor armature 3, however, it is necessary to select the material and to design the structure so that it can withstand the centrifugal force generated by the rotation thereof, as well as taking into account the electromagnetic characteristics. The conventional rotor armature has not achieved a satisfactory structural design capable of withstanding the centrifugal force since such designs only take into account the electromagnetic characteristics. Accordingly the conventional rotor has the limitation that the highspeed rotation depends on the tensile strength of the rotor armature, so that it is difficult to realize rotors capable of higher speed rotation. Although it is desirable to use a material having both excellent electro-magnetic and mechanical characteristics for the rotor armature, such materials are hard to obtain as a practical matter. It is an object of the present invention to eliminate the above-noted drawbacks and to realize a rotor capable of higher speed rotation and which is comprised of a soft magnetic laminated plate having an excellent electromagnetic characteristic in order to improve the electromagnetic conversion efficiency and which uses a material having an excellent mechanical strength in order to strengthen the mechanical strength of the rotor.